Make sure you have done this to Reset the shuffle, since this problem occurred
Looks like you use a Mac... When you connect the iPod with iTunes NOT running, then run Disk Utility, does your shuffle's disk appear in the Disk Utility sidebar?
Also, which shuffle model do you have? This document shows the four types
Does the light on the side of the shuffle come on when connected? If it does not, make sure the USB cable's plug is completely inserted into headphones jack. The USB cable you are using is the short one that came with the shuffle, correct?
As a test, you may want to shut down (power off) the Mac and disconnect all USB devices, including any hubs. Start up with only standard keyboard and mouse connected (if normally used). Do the Reset again on the shuffle
Run iTunes. Connect shuffle to a direct USB port on the Mac.
If that does not help, connect something else to the USB port to confirm it is working properly, preferably something similar to the shuffle, such as a USB flash drive.
Very strange. Here's what happened:
The light on the side did not come on. Checked the connection (yes, short cable) -- OK. did the shutdown, Reset, tried again, nothing. Tried a different device on the port -- no problem.
Then, just out of frustration, I plugged the shuffle back in and the blinking orange light appeared. Sure enough, iTunes now recognized it! I was able to sync and see all the info about the device. This time I ejected it properly.
A couple of minutes later, I tried again. Nothing! No blinking light, no recognition.
What do you suppose is going on??
That's odd... What happens if you plug that other device in the USB port again, then disconnect it and connect the shuffle again? Might as well repeat the actions that made it work, to see if there are any clues...
It might be something about the USB cable's connection at either end. Maybe the plug at the USB end or the iPod end is slightly worn, and not connecting reliably every time. Be sure to try another direct USB port.
Also, if you have one, connect a self-powered USB hub to the Mac and connect the shuffle to the hub. "Self-powered" means that it has its own power supply. This will test to see if there is some kind of "lack of power" issue on the USB port. If the hub makes it work reliably, you can try doing this Reset SMC procedure
which resets the Mac's "power management." You can try the Reset SMC procedure even if you didn't use a USB hub as a test, to see if that makes a difference.